identification ? [solved]

Hi

Does anyone have an idea what this could be?

Weight, diameter (the largest), thickness (at the center) and estimated alloy, please?

- nonmagnetic

- waight : 4.2 g

- diameter:  about 22mm / 19mm

- thickness: about 2 mm

thanks!

 Only the front looks original - the back just looks to have been scratched in. 

Therefore, it is like this > 

N#345927 [same 22mm size] 

I think you're right. 

However, the back doesn't look scratched.

 It's probably some kind of symbol, but it'll be difficult to determine what it is.